Unsaturated fatty acid is a fatty acid containing one or more double bonds, and mostly is liquid at room temperature. Highly unsaturated fatty acid generally indicates a fatty acid containing four or more double bonds per molecule, and recently, many physiological functions thereof have been reported. Particularly, an omega 3-fatty acid in unsaturated fatty acids exists in nerve cell membrane and retina, and plays a role to rapidly transfer electric stimulus from a cell membrane to another cell. It has been reported that an omega 3-fatty acid has an effect to protect cells in body, keep the structure of cells, and help the metabolism smoothly. Also, it has been reported that an omega 3-fatty acid is effective for inhibiting formation of membrane of blood, and stimulating formation of bones and strengthening bones at the same time.
As the kinds of omega 3-fatty acid, there are docosahexaenoic acid (DHA), Eicosapentaenoic acid (EPA), Docosapentaenoic acid (DPA), etc. Particularly, EPA increases the fluidity of blood to inhibit formation of thrombus and to decrease cholesterol value in blood that is the cause of arteriosclerosis. Clinical tests to EPA refined from fish oil showed that increase of EPA in blood results in decreasing cholesterols in blood and inhibiting agglutinations of platelet.
Also, it has been reported that EPA is effective for the prevention and treatment of atopic dermatitis, bronchial asthma, and allergic disease such as pollen allergy, and for the treatment of inflammatory disease such as chronic arthritis.
DPA is known as noticeable next generation material, and also known to be more effective for circulatory system diseases than DHA or EPA. It was confirmed in animal tests that DPA inhibits the receptor of vascular endothelial growth factor, KDR. Thus, medical centers have noted DPA for inhibition of vascularity. Also, DPA has been developed for the treatment of metabolic diseases because it is effective for emigration of vascular endothelial, inhibition of formation of thrombus, and metabolism of carbohydrate.
Omega 3-fatty acids are encouraged to take 0.6˜1 g per day, and contained in fish oil, plankton, marine products, bean oil, mother's milk, etc. Particularly, more amounts of omega 3-fatty acids are required for newborn baby and young people for normal development of tissues. Recently, omega 3-fatty acid has received a huge attention because it is known that its deficiency may cause depression, schizophrenia, attention-deficit hyperactivity disorder, vision decline, cardiac disease, etc., and may aggravate stress.
But, unsaturated fatty acids are easily oxidized by oxygen or light. Particularly, highly unsaturated fatty acids are oxidized during storage, to emit unique fishy smell. To improve this problem, many studies for capsulation of unsaturated fatty acids have been conducted.
In capsulating unsaturated fatty acids, capsule material should have excellent film forming ability to protect unsaturated fatty acids and low viscosity of emulsion. And, unsaturated fatty acids in capsules have to be dispersed uniformly and finely in emulsion state.
In the case of puverization of capsule, the efficiency of microcapsulation depends on the form of used capsule material, and is the most important element to affect the emulsion's stableness before drying, the physical stableness after drying, and the storage term. And, capsule materials affect solubility, emulsification, membrane formation, and drying property. Thus, capsule materials used for pulverization of unsaturated fatty acids such as omega 3-fatty acids are very limited.
And, the degree of capsulation of unsaturated fatty acids depends on physical property of unsaturated fatty acids, and the property and state of unsaturated fatty acids depend on combination method and combination rate in functional foods. Thus, there are many difficulties in applying capsules of containing unsaturated fatty acids to articles.
Also, it has been needed to pulverize capsulated unsaturated fatty acids in order to apply unsaturated fatty acids having many merits as above described, to various products.
Capsulating methods of highly unsaturated fatty acids for utilizing the merits of capsule have been reported. For example, Noh et al. (Korean Patent Publication No. 2000-0038444) disclosed a method to improve physiological property of fish oil by a capsulating method of highly unsaturated fatty acids such as DHA (docosahexaenoic acid), through using polysaccharide like glutinous rice starch, and emulsifying agents like twin series. But, this method has disadvantages that the dispersibility of fish oil cannot be maintained in water solution for a long time, and the heat stability (20° C.) is lowered.
Park et al. (Korean Patent Publication No. 2004-0042987) disclosed a method of capsulating fish oil containing highly unsaturated fatty acids by using soy protein, a protein kind of coating material, etc., applicable to many fields including food, but the unstability of capsule is a disadvantage of the method.
Also, many soft capsules containing highly unsaturated fatty acids have been developed. But, soft capsules give an image like medicine in oral administration, and so are offensive, particularly for children. Thus, there have been many studies about tablet form of unsaturated fatty acids from the point of industries and users, but no clear solutions have appeared yet.